(a) Field of the Invention
The present invention relates to a semiconductor device, and particularly to a bonding pad included in a semiconductor device and a formation method of the bonding pad.
(b) Description of Related Art
In general, a bonding pad is formed as an exposed part of the uppermost metal wire of a semiconductor device and serves as a terminal to connect the semiconductor device to a package. That is, wiring of the semiconductor device is electrically connected to an external device such as power supply via the bonding pad connected to a metal wire by bonding process.
FIG. 1a is a sectional view of a conventional bonding pad, and FIGS. 1b and 1c are sectional views of the boding pad to explain bonding process and molding process, respectively.
For every semiconductor device, the last process of fabrication is the process of a forming bonding pad 3 by exposing a portion of a metal wire layer 1. Then, back grinding process and package assembly process are continued. Through the assembly process, the metal wire layer 1 and a metal wire 7 are bonded to each other by soldering 5, and the connection point of the bonding pad 3 and the metal wire 7 are molded using a molding material 9 such as epoxy.
However, for the conventional bonding pad 3, contact area between the exposed metal wire layer 1 and the soldering 5 is narrow. Therefore, bonding defects easily occur due to imperfect bonding. Also, moisture might penetrate into the insulating layer 11, which is an oxide layer, when molding using a molding material such as epoxy.
Prior arts disclosing subject matters related to bonding pad, adhesiveness, and moisture include the following U.S. patents.
U.S. Pat. No. 6,471,115 discloses a formation method of an electronic circuit device using solder material as an electrode or an electrical part on a printed circuit board, U.S. Pat. No. 6,376,353 discloses a process for placing a specific Al—Cu bond layer or area on a copper pad, U.S. Pat. No. 6,191,023 discloses an aluminum bond pad structure for improving adhesiveness between a copper pad and a tantalum nitride pad barrier layer using a special interlocking bond pad structure, U.S. Pat. No. 5,923,072 discloses a semiconductor device including a metal passivation film formed between a portion of surface of a metal pattern and moisture penetration path, U.S. Pat. No. 5,430,329 discloses a semiconductor device having an elastic insulating film covering inner surface of a pad electrode opening, and so forth.